Το πρώτο σύμπτωμα ήταν ναυτία, και μετά είχα και λίγο ρίγος το βράδυ.

Because it has to agree with σύμπτωμα.

• σύμπτωμα = symptom
• It is neuter singular
• So the adjective πρώτος / πρώτη / πρώτο becomes πρώτο

So:

• το πρώτο σύμπτωμα = the first symptom

This is normal Greek adjective agreement: the article, adjective, and noun all match in gender, number, and case.

It means the first symptom.

Breaking it down:

• το = the for a neuter singular noun
• πρώτο = first
• σύμπτωμα = symptom

So the phrase is a straightforward noun phrase: the first symptom.

ήταν is the imperfect form of είμαι (to be), and here it means was.

So:

• Το πρώτο σύμπτωμα ήταν ναυτία = The first symptom was nausea

Greek often uses the imperfect of είμαι for background description in the past, just as English uses was.

Because Greek often leaves out the article with illnesses, symptoms, or abstract conditions when speaking generally.

So:

• ήταν ναυτία = it was nausea

This is natural Greek. You could sometimes see an article in other contexts, but here the bare noun sounds normal.

Useful comparison:

• Έχω πυρετό = I have a fever
• Έχω πονοκέφαλο = I have a headache
• Ήταν ναυτία = It was nausea

Greek often treats these as symptom words rather than fully definite nouns.

Because έχω means to have, and είχα is its imperfect past form.

So:

• είχα = I had / I was having

In this sentence:

• μετά είχα και λίγο ρίγος = then I also had a little chills / some chills

The imperfect is common in narration about how symptoms developed over time.

The two και do slightly different jobs.

1. The first και simply links clauses:

   • ..., και μετά ...
   • ..., and then ...

2. The second και adds the idea of also / too / as well:

   • είχα και λίγο ρίγος
   • I also had a bit of chills

So the sentence means something like:

• The first symptom was nausea, and then I also had a bit of chills in the evening.

That second και is very common in spoken Greek.

λίγο ρίγος means a little chills or more naturally in English a bit of chills / some chills.

Why λίγο?

Because ρίγος is a neuter singular noun, and λίγος / λίγη / λίγο must agree with it.

• masculine: λίγος
• feminine: λίγη
• neuter: λίγο

So:

• λίγο ρίγος = a little chill / some chills

Even though English often prefers the plural chills, Greek commonly uses the singular noun ρίγος.

ρίγος means chill, shivering, or chills in a medical/physical sense.

In context, it refers to the feeling of trembling or being cold because of illness.

So:

• είχα λίγο ρίγος = I had some chills

It is a useful symptom word in Greek.

το βράδυ means in the evening / at night / that evening, depending on context.

Greek often uses the accusative for expressions of time, and the article is very normal in these time phrases.

Examples:

• το πρωί = in the morning
• το μεσημέρι = at noon / in the afternoon
• το βράδυ = in the evening / at night

So here:

• είχα και λίγο ρίγος το βράδυ = I also had some chills in the evening

This is a very common structure.

Not exactly in the same way as English after followed by a noun phrase. Here μετά means then / afterwards.

So:

• και μετά είχα... = and then I had...

If Greek wants to say after + something, it often uses:

• μετά από
  • noun
• μετά που / other structures in some contexts

For example:

• μετά από μία ώρα = after an hour
• μετά το φαγητό = after the meal

But in your sentence, μετά works as an adverb meaning then or afterwards.

Because Greek usually does not need subject pronouns when the verb ending already makes the subject clear.

• είχα already means I had

So Greek often drops εγώ (I) unless it is needed for emphasis or contrast.

Compare:

• είχα λίγο ρίγος = I had some chills
• εγώ είχα λίγο ρίγος = I had some chills (with extra emphasis on I)

This is one of the biggest differences from English.

The given word order is natural, but Greek word order is fairly flexible.

Original:

• Το πρώτο σύμπτωμα ήταν ναυτία, και μετά είχα και λίγο ρίγος το βράδυ.

This is a normal narrative order:

1. first symptom
2. then what happened next
3. time expression at the end

You might also hear slight variations such as:

• Το πρώτο σύμπτωμα ήταν ναυτία και μετά το βράδυ είχα και λίγο ρίγος.

That said, the original sounds smooth and natural. Greek often moves words around for emphasis, but the version you have is perfectly standard.

It sounds natural and everyday, while still using normal symptom vocabulary.

• σύμπτωμα is a common word and can sound slightly more descriptive or organized, as if someone is explaining how an illness started.
• ναυτία and ρίγος are standard words you would hear in normal conversation, at a doctor’s office, or when describing symptoms.

So the sentence is not overly technical. It sounds like a person calmly explaining how they felt.